Laser-induced plasma spectroscopy (LIPS) is a method known in the art for analysis of elements present in a sample, typically a liquid sample. Apparatus and methods for LIPS are described, for example, in U.S. Pat. No. 4,925,307, to Cremers et al., and in U.S. Pat. No. 5,379,103, to Zigler, both of which are incorporated herein by reference.
In a typical LIPS system, a high-intensity pulsed laser beam is focused at or near an upper surface of the sample, creating a breakdown spark. The spark causes a plasma cloud to be blown off the sample. Excited elements from the sample in the plasma cloud emit characteristic spectral radiation. A portion of the emitted radiation is collected by an optical system and focused into a spectrometer and optical detector. A spectrum of the radiation is analyzed to determine the elemental composition of the sample.
The plasma cloud formation is typically accompanied by a shock wave propagating off the sample at high, even supersonic, speed. Particles from the sample are sprayed in all directions and may impinge on elements of the optical system. These elements must therefore be cleaned frequently if the LIPS system is to work properly.